Automatic telephone system



A. B. SMITH AUTOMATIC TELEPHONE SYSTEM Nov. 20, 1923. 1414; 48-

Filed Oct. 1, 1920 3 sheetssharp fif'i'hur 55551 SE.

Nov. 20 1923. 1,474,648

A. B. SMITH AUTOMATIC TELEPHONE SYSTEM Filed Ooh I 1920 2 Sheets-Sheet 2 Patented Nov. 20, 1923.

UNI-TED STATES,

PATENT OFFICE.

ARTHUR BESSEY SMITH, OF EVANS'ION, ILLINOIS, AS SIGNOR TO AUTOMATIC ELEC- TRIO COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

nuroma'rrc TELEPHONE SYSTEM.

Application filed October 1, 1920. v Serial No. 414,080.

To all whom it may concern:

Be it known that I, ARTHUR BESSEY SMITH, a citizen of the United States of America, and a resident of Evanston, Cook County, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My inventionrelates in general to automatic telephone systems and more specifically to an improved type of secondary line switch or secohdary nonnumerical rotary.

. such a case these trunk lines usually terminate in incoming line switches in the mainv exchange which are operated to aut0mat1- cally select one of a plurality of selectors in the main exchan 'e. 1

Among the ob ects of my invention are, to provide an improved type of rotary switch for use in such a system and one which materially speeds up the service. Also I provide a simple type of secondary line switch which has a new and highly'improved method of testing and operating.

The improved line switch which I have devised perm'its'the selector which seizes it to test not only the 'line switch but also to test the trunk line upon which the line switch stands. 7

In Fig. 1 of the drawings I have shown a calling stationA of the usual automatic type comprising the usual talking equ1p ment and a calling device of the standardtwo wire Stowger type, having individual thereto a line switch C of standard rotary type whose wipers have no normal position and which stand on the trunk line last used.

This line switchC has access to a plurality of first selector switches such as that shown In Fig. 2 I have shown at'E a secondary -line switch of my improved t pe which is accessible to the selector D. ig. 1) from one level. It is to be understood that the selector D has access to connector switches of standard type. from other levels of its bank for calls local to its own exchange. This line switch E is similar in its mechanical construction to the line switch C (Fig. 1) in that it has wipers which move onl in one direction and which normally stan on the trunk line last used. The circuits for controlling. this switch E difl'er materially from those of the switch C- however, and will be described in detail later on. I This line switch E has access to selector switches of standard type such as thatzshown at F which in turn may connect through other selectors and connectors to called-subscribers line.

I will now describe in detail the operation ofmy improved system when a call isinitiated by the subscriber A. The operation of the. line switch G and the selectors -D and F will be described more or less generally as such switches are well known In the art and have been thoroughly described in prior patents.

\Vhen the subscriber at A' removes his receiver to initiate the call a circuit is completed over the-two sides of the calling line in series with line relay'2 and battery. Relay 2 energizes to complete a series circuit of switching relay 3 and rotary magnet 4. A

circuit is completed at the same time from the private wiper 5 direct to'the rotary magnet 4, so that if the trunk line upon which the wipers now stand is busy, ground will be present on the private terminal thereof and acircuit will be completed through rotary magnet 4, shunting relay 3 in said series circuit, and the magnet 4 will operate to step the wipers to the next trunk line. is reached, relay 3 will be no longer short circuited and will energize over said series circuit to disconnect line relay2 and ground from the line circuitand extend the same via wipers 6 and 7 to the relay 8' of the selector D. Relay '8 energizes over the As soon as an idle trunk line series circuit including the calling line and operates to close a circuit for slow release relay 9, which in turnoperates to the release trunk to hold the line SWItCh' C ound ground at springs of relay 9 through springs 12 and 13, through ofi' normal springs 14, as soon as the first vertical step is taken, and

through relay 15 to battery. Relay 15 pulls up to close one point at springs 16 in the circuit of rotary magnet 17 and locks itself energized from ground through springs 18 and springs 19 of rotary magnet 17,

Should the called party be located in the same branch exchange then it will be un derstood that the selector D will be operated to some level in which are located trunks leading to connector switches in the branch exchange or to second selectors, and the call will proceed in the usual manner. However, assuming that the called party is located in some other exchange, then selector D will be operated to the level in which the trunk lines leading to that exchange are located.

Returning now to the operation of the selector D, as soon as relay 1O falls back after this first series of impulses a circuit is completed for the rotary magnet 17 from ound through springs 20, springs 12 and 21, and springs 16. Magnet 17 operates to step the wipers into connection with the first trunk line in the level and opens the circuit of relay 15 at springs 19. Relay 15 in turn falls back and opens the circuit of the rotary magnet at springs 16. The private wiper 21 now rests on the private contact of the trunk line leading to the first of the rotary switches E and as soon as magnet 17 falls back a new circuit is closed for relay 15 extending from battery through said relay, springs 14, springs 19, springs 22 and 23, wiper 21, contact 24, conductor 25, low resistance upper winding of relay 30, and private wiper 35 of switch E. Assuming that the switch E is idle but is resting on a busy trunk then ground will be present on the contact on which wiper 35 is resting. The circuit of relay 15 will therefore be completed and the relay will operate to again close the rotary magnet circuit to step the switch onto the next rotary switch E. This operation will continue until an idle switch E is found which is resting on an Iai dle trunk line leading to a selector such as Should the switch E (first tested) have been busy, due to its seizure by some other elector D, then the circuit for relay 15 Would have beencompleted to the wiper 35 and ound through the front contacts of rela 30 of the switch E aswill be later descri ed.- v

Assoon as selector D finds such idle switch there will be no circuit for relay 15 and a circuit will become efl'ective for the switching relay 26 of selector D from ground through springs 20, relay. 26, springs 19, springs 14, and relay 15 to battery. Relay 26 being of comparatively high resistance will energize alone over this circuit and will switch the connection direct to the conductors 27 and 28 leading to the seized switch E. Relay 26 was maintained short circuited in this circuit as long as wiper 21 found ground on busy trunks. Relay 26 upon energizing connects ground direct from springs 20 to the wiper 21 through spring 23 and its front contact. A circuit is now completed from this ground over wiper 21, contact. 24, conductor 25, low resistance winding of relay 30, and through relay 33 to battery. Another branch of this circuit may be traced through high resistance 36, and lower high resistance winding of relay 30 to battery. Relay 30 is so wound that both windings assist each other at this time and relay 30 will therefore attract its armature to close the springs 37 and 38 in the talking circuit, thereby completing the circuit of line relay 44 of selector F. The above traced circuit of relay 30 now is changed over by the attraction of armature 39 and is as follows, ground over wiper 21, conductor 25, springs 40 and 41, spring 39 and lower winding of relay 30 to battery, a branch of this circuit also passes from springs 41 through relay 33 to battery. Relay 30 is therefore held energized by its lower winding and as soon as line relay 44 of switch F energizes and in turn operates slow relay 42 then ground will be supplied through springs 43 of said relay over the release trunk and wiper 35 to hold relays 3O 1 and 33 energized, andv to hold switches (l and D in operated position. The selector F may now be controlled, in the same manner as was the selector D, in accordance with the second digit of the called number to extend the connection on toward the called party.

Returning now to the rotary switch E,

there is provided a common or master relay 32 the purpose of which is to maintain one of the group of switches E always in connect1on with an ldle trunk line.

This relay 32 has a circuit controlled by a chain of relays 33, 34, etc., one of which is individual to each switch E. It will be seen that relay 33 will be energized whenever the switch E is either in use or is resting on a busy trunk line. Now when all of the relays 33 and 34, etc., are energized, that is when all switches E are inaccessible to selectors D, then the circuit of relay 32 will be completed by these chain relays and will operate to connect battery to one side of all the rotary magnets 31 of the switches E. Now it will be seen that any switch E which is in use will have the circuit of its magnet 31 opened at springs of relay and will therefore not be a ected in any way. However, all line switches which are idle and whose wipers are standing on a busy trunk line will be rotated in search of an idle one. That is, the circuit of magnet 31 will be closed from batterythrough armature and front contact of relay 32, magnet 31 and its interrupter'springs, springs of relay 30 .wiper 35, and ground on the busy trunk line. This common relay 32 in combination with the chain relays will therefore insure that there will always be one of the switches E standing upon an idle trunk line and accessible to a selector D.

Vhen the selector D is testing trunk lines to switches E and the switch E although idle is resting on a busy trunk'line, then as explained, a circuit was closed from ground at wiper 35 through the upper winding of relay 30 and through the rotary interrupter relay 15 of selector D to battery. At the same time a circuit was completed from ground at wiper 35 through resistance 36 and lower winding of relay 30 to battery. At this timercurrent will flow in opposite directions through the two windings which therefore oppose each other magnetically and. prevent the operation of the relay.

It will thus be seen that I have designed a novel nonnumerical switch for use as a secondary trunk selecting switch which is very simple in construction and which materially speeds up the action of such rotary switch. Also that this switch permits the selectors which seize it to not only test it for busy but also to test the trunk line upon which it stands.

will always be standing on an idle trunk unless all are busy.

Have thus described the details and operation of my system, what I consider to be new and desire to have rotected by Letters Patent-will be set fort in the appended claims.

lVhat I claim as my invention is:

1. I11 a telephone system, a nonnumerical switch having wipers which normally stand on the trunk line last used, a selector for seizing said line switch, and means for preventing the seizure of said switch whenever the switch is busy or whenever the switch is idle and the trunk line upon which the wipers are standing is busy.

2. In a telephonesystem, a nonnumerical switch having wipers which normally stand;- on the trunk line last used, a selector for seizing said line switch, and means for causing said switch to test busy to said selector whenever it is in use and also whenever it is idle but is standing on a busy trunk line. r

3. In a-telephone system, 'a nonnumerical switch,trunk lines accessible thereto, wipers Means is also provided so that one or more of these switches for said switch which normally stand on the trunk line last used, a selector fortesting,

and seizing said non-numerical switch. and means always operative for causlng said selector to slmultaneously test the switch and the trunk line upon which its wipersthe trunk line last used, a test contact and' a test wiper for said switch, and a normally closed circuit extending from the test contact to the test wiper so that if the trunk line, upon'which the wipers of the switch stand, is busy and ground is connected to the test contact thereof, said ground will also be present at the test contact of said switch.

6. In a telephone system, a nonnumerical automatic switch having trunk lines accesslble thereto and wipers whlch always stand on one of sald trunk lines, and means for making said switch busy whenever the trunk line upon which the wipers are standing is busy. J

7. In a telephone system, a nonnumerical automatic switch having trunk lines accessible thereto and wipers which always stand on one of said trunk lines, means for making said switch busy whenever the trunk line upon which the wipers are standing is busy, and means controlled from the trunk line upon which the wipers are standing for causing said switch to automatically select an idle trunk line. I

8. In a telephone system a nonnumerical switch, trunk lines accessible thereto, and

wipers for said switch which always stand on one of said trunk lines, the busy or idle condition of said switch depending upon {he busy or idle conditionof said one trunk 9. n a telephone system a group of non-L numerical switches, trunk lines, accessible] thereto, said switches each having wipers ,12'0 which normally stand on the contacts of one of said trunk lines, and means common to said switches for maintaining one of said switches always in connection with an idle trunk line while other of said switches are standing on busy trunk lines. l

-10. In a telephone system a group of-nonnumerical switches, trunk lines accessible.

thereto, said switches each having wipers which normally stand on the contacts of .one

trunk line.

12. In atelephone system, nonnumerical switches, trunk lines accessible in common to said switches wipers for said switches normally standing on a plurality of said trunk lines, and means controlled when the trunk lines upon which all of the switches are standing are busy for causing an idle switch to automatically rotate in search of an idle trunk.

Lil

13. In a telephone system, a nonnumerical switch, a test wiper for said switch and a test contact therefor, a relay for said switch. a circuit for said relay including the test contact and the test wiper, another circuit including only said test contact, and a branch circuit for rendering the first circuit inoperative and the second circuit operative.

14. In a telephone system, a nonnumerical switch, a test wiper and a test contact therefor, a test circuit for the switch including the test wiper and contact, a relay connected to said test circuit, means for applying a guarding potential to said test wiper while the switch is idle, ,means for making said testcontact test busy and for preventing any operation of said relay whenever said guarding potential is connected to said .wiper, and means for operating said relay whenever the switch is tested and no guarding potential is present on said test wiper.

15. In a telephone system, a plurality of auton'iatic switches, trunk lines accessible in common to said switches, wipers for said switches which normally stand oira plurality of said trunk lines, means fo'i making all of the trunk lines upon which the use. '1 17, ha telephone system a series of autoswitchesare standing busy, and means controlled by the busy condition of all of said trunk lines for causing s'omeof said switches to automatically operate to find an idle trunk independent of the seizure of any of the switches. t e

16. In a telephone system, subscribers lines, automatic switches of two classes having selectively movable wipers, 'an d means for es-' inat'ic switches operated successively to establish a connection. wipers for each switch, the wipers ot' the second switch always standing on the contacts of a trunk line, means for operating the first switch of the series to automatically select. an idle second switch, and iiieans for preventing seizure of any second switch whose wipers are standing on a busy trunk line. I

18. In a telephone system, a non-numerical trunk hunting switch having a test wiper and line wipers which normally stand on the corresponding contacts of a trunk, said switch having a test conductor and line conductors corresponding respectively to said wipers, said test conductor being normally conductively connected with said test wiper, means. for seizing said switch, and means controlled over said test conductor for preventing the seizure of said switch regardless of whether said switch is busy or idle when a busy potential is impressed upon the test contact upon which said test wiper is standing. I

19., In a telephone system, two serially related automatic switches and a trunk line, a test contact individual to the second switch accessible to the test Wiper of the first switch, a test contact individual to said trunk line engaged by the test wiper of said second switch, a'nda metallic connection between the test contact andtest wiper of said second switch, whereby the said first switch may be operated to test the said trunk line by way of said test contacts and test wipers.

2O. In a telephone system, means including two directively controlled switches for completing a connection, a non-directive hunting switch interposed between said switches, and circuit connections including a wiper of said hunting switch to enable the first directive switch'to'testthe second directive switch and determine whether' the same is busy or idle.

21. In a telephone system, an automatic progressively movable switch, a differential switching relay in said switch, a test circuit completed when the said switch is busy, at

second test circuit completed when the switch 'is idle, and suitable circuit connections .be-

tween the two windings of said relay and the said circuits such'that the said windings oppose each other when the first circuit is closed and assist each other when the second circuit is closed. v i 22. In a telephone system,' a plurality of automatic trunk hunting switches each having a test wiper, a motor magnet in each switch having one terminal normally connected to the associated test wiper, the other terminals of said magnets being'normally disconnected, means for connecting a source of current to the said test wipers when the trunks on which said wipers are standing become busy, and means for connecting the normally disconnected terminals of said magnets to said source to cause said switches to hunt for idle trunks.

23. In a telephone system, a plurality of automatic trunk hunting switches each having a test Wiper, a motor magnet in each switch having one terminal normally connected to the associated test Wiper, the other terminalsof said magnets being normally 1 disconnected, means for connecting a source of current to the said test wipers when the trunks on which said Wipers are standing become busy, and means including a relay common to all of said trunks for connecting the normally disconnected terminals of said magnets to said source to cause said switches to hunt for idle trunks.

Signed by me at Chicago, Cook County, Illinois, this 29th of September, 1920.

ARTHUR BESSEY SMITH. 

